|Computer SIG Meeting - 10 October 1998)
Doug Hay and Elizabeth Rodier
Computer Special Interest Group (SIG)
Scanners can be used for digitizing line drawings, clip art and
photos or for converting text to editable files (called Optical
Character Recognition or OCR).
Like everything else what to buy depends upon what you want to
do with the scans:
- for internet publishing a low resolution, cheap scanner is fine
- for reproducing photos at the same size, a higher resolution
scanner would be required
- for enlarging photos, or picking heads from a group picture,
a better scanner is necessary.
Prices range from $100 to well over $1000 (Cdn).
Types of Scanners
No longer sold new. They do an adequate job for most normal uses.
Scan to 400 dpi. The limitation is they only scan 4 inches wide.
You must stitch successive scans together for larger originals.
Can be very small for portability. Sometimes combined with a fax
and printer (about $800). They are usually only 24 bit color and
are limited to single sheets.
These are the most versatile, able to scan book pages and anything
you can lay on a glass sheet. Most have optional accessory to scan
negatives or slides.
Bits of colour vary from 24 on lower priced models to 30 on intermediate
and 36 on top of the line models. 30 bits is adequate for most jobs.
36 bits often doesn't cost much more and it will give you a difference
in color density in the darker areas.
DPI or dots per inch is a measure of the detail. The dpi are quoted
as optical/hardware and interpolated/enhanced. The optical is what
is actually scanned. Software gives you an apparent to the eye enhanced
image, but there is not any more detail. Optical varies from 300
to 600 dpi and enhanced resolutions are quoted as high as 9600.
If you are using a color printer, there is no use scanning at any
greater than your printer's dpi. Often 100 dpi is high enough. Most
printers print at an optimum dpi somewhere between 75 and 200. The
size of your scanned file quadruples for every doubling of dpi.
For instance a 4 x 6 color photo scanned at 100 dpi is 700 kb, 200
dpi is 2.8 mb, 400 dpi is 11.3 MB.
Scanners can be hooked by a SCSI board or parallel port. SCSI requires
installation of a card in your computer and costs about $30 more
than a parallel, but is significantly faster. A parallel connects
directly to your printer port. Most have a port in the back to connect
your printer to.
Prices vary from $100 to near $1000. A good solid performer should
not be more than $400. The ones with the best reputations are:
The Plustek does negatives and slides also.
The prices are list and there are often rebates available.
The lowest price one I have seen is the Storm EasyPhoto with
600 x 300 resolution at $112 (some people tell me it does a
Each scanner comes with all the software neccessary to scan, edit
and store as well as OCR. The quality and complexity of software
varies, but all will do an adequate job for a beginner. If you really
get into it you can buy add-on software, the best of which may cost
you more than the scanner. Photoshop for photo editing and Textbridge
for OCR are the top sellers.
Because color scan files are so large, you should have at least
32 MB of RAM. (Cost about $50). You should have at least a 166 Mhz
speed. Slower chips work OK but you might get tired waiting for
them. Most scans will not fit on a 1.44 MEG floppy disk, unless
compressed, so either a huge hard drive or an off-site storage such
as a ZIP drive ($180) will be required if you do much scanning.
There are 3 main types of file format:
- TIF for continuous tones (photos) gives the
best quality and maximum compatibility with other software. But
they are the largest size.
- GIF for line art and graphics this gives the
best quality and a smaller size file.
- JPG can give you great compression (up to 90
%) but you lose a little quality every time you compress or open
the file. It won't work well for line art. For email or web pages
it is almost a must because of the size.